Hydraulic cushion



. Feb. 4, 1936. F. J. RODE HYDRAULIC CUSHION Filed June 8, 1955 i lln k llIH llll

Patented Feb. 4, 1936 HYDRAULIC CUSHION Fredrlch J. Rode, Toledo, Ohio Application June 8, 1935, Serial No. 25,890

7 Claim.

This invention relates to hydraulic cushions, and is more particularly directed to a self-contained unit adapted for use with sheet metal presses in which the metal is shaped between cooperating dies, one of which reciprocates toward and away from the other, the work being clamped by a blank holding element that cooperates with the reciprocating die member and which is resisted in its movement in one direction by the cushion.

It has heretofore been proposed to build a hydraulic cushion into the bed of a press in such a manner that the space surrounding the cushion cylinder constituted a liquid reservoir. Liquid was forced out of the cylinder, into the reservoir, on the working stroke of the press and was returned by pneumatic pressure after the forming operation was complete. Such a device is disclosed in my Patent No. 1,773,438, dated August 19, 1930. Devices 01 this character are satisfactory if a convenient source of pneumatic pressure is available. However, they are attended by the disadvantage that it is necessary to control and work with two kinds of fluid pressure.

The primary object of the present invention is the provision of a self-contained cushion bed in which no pneumatic pressure is used, and in which the cushion parts are returned by hydraulic pressure alone.

Another object of the invention is the provision of a device of this character, in which the hydraulic pressure source is constantly operated under controlled conditions.

Other objects and advantages of the invention will become apparent as the description proceeds, reference being had to the accompanying drawing, in which- Figure 1 is a fragmentary elevational view, with parts in section, of a press equipped with one form of the invention, and Fig. 2 is a fragmentary sectional detail of another form of the invention.

Referring to the drawing, I designates the bed of a press having spaced uprights 2 between which a reciprocating slide '3 is mounted for movements in the usual manner. The plunger 3 carries a movable die member 4 which is adapted to cooperate with a stationary mating die 6 mounted in any suitable manner on the bed.

A blank holding ring 8 surrounds the stationary die 6 and cooperates with the movable die 4 to clamp the sheet metal to be formed by the dies.

It will be appreciated that these parts so far described are conventional and well known in the art and form no part of the present invention. The cushioning device with which the present invention is particularly concerned inclflzudes a piston I which operates in a cylinder a space It formed in the bed I and which "is adapted to act as a reservoir for the body of liquid used in the cushion. Suitable ports 16 open into the reservoir l4 and communicate with the interior of the cylinder 12 through the body of a centrifugal pump having vanes l8 mounted on an operating shaft 20 driven by an electric motor 22. It will be seen that in the form shown in Fig. l, a single stage pump is used having intake passages 24 at the top and bottom and a discharge passage 26 opening into the interior of the cylinder I2. Thus, the pump acts to force 011 from the reservoir I 4 into the interior of the cushion cylinder.

The motor driven centrifugal pump is constantly operated so that the piston I0 is urged outwardly of its cylinder by constant pressure created by the pump. When the piston dwells at its upper limit during the upstroke of the press,

. the pump merely rotates in the oil and maintains the pressure against the piston. When the slide 3 moves down .to force the blank holding ring 8 and piston ID downwardly, the liquid is forced outwardly past the vanes of the pump into the reservoir l4. However, as soon as the pressure of the slide is released, the pump again acts to return oil into the cylinder l2 from the reservoir M. It will be seen that the pressure set up by the pump is proportional to the speedof the vanes so that the pressure can be lowered or raised by changing the speed of the motor 22. In the instance of a direct current motor, such change in speed may be readily made by-a variable resistance R, while in an alternating current motor, such pressure change may be accomplished by changing the path of the current through the motor, or in any other known manner.

The pressure on the piston may also be varied by changing the design of the centrifugal pump in various ways, as by providing a multi-stage pump as shown in Fig. 2. In this instance, the first stage of the pump is provided with a centrally disposed intake opening 30 and a discharge port 32 which communicates with the second stage of the pump through an intake opening 34. The second stage of the pump discharges through a port 36 directly into the cylinder l2 of the cushion. Obviously, as many stages of pumping operation may be provided as become necessary The cylinder 12 is in. communication with tocreatethedesiredpressureinthe cushioncylinder.

It will be appreciated that numerous modifica-v tionsandchangesmaybemadein theformof the centrifugal pump emp y M01! 9 visions for speed control of the pump driving motors also made. It should be expressly understood that such modifications and changes are included in the scope of the present invention as deflned in the appended claims.

Having thus described my invention, what I claim as new, and desire to secure by United States Letters Patent, is:

1. In a press of the class described, movable blank holding means, a piston connected to said means, a cylinder in which said piston operates, and a centrifusfl v Dump Operable to constantly suppLv fluid pressure to said cylinder to act on said piston to resist movement thereof in one direction, said pump being in constant and open communication with said cylinder.

2. In a press of the class described, movable blank holding means, a cylinder, a piston operating in said cylinder and connected to said means, and a centrifugal pump operable to constantly supply hydraulic pressure to said piston to resist a movement of the piston in one direction, said pump being in direct and open communication with said cylinder.

3. In a press of the class described, movable blank holding means, a cylinder, a piston working in said cylinder and connected to said means to resist movement thereof in one direction, a hydraulic pump in said cylinder in opposition to said piston, a fluid pply reservoir for said pump, and means for operating the pump to apply predetermined pressure against said piston to resist movement thereof in one direction.

4. In a press of the class described, movable blank holding means, a cylinder, a piston movable in said cylinder and having connection with said means to resist movement thereof in one aoaassv direction, a fluid supply reservoir in communication with said cylinder, and means including a centrifugal pump for acting on fluid in said reservoir to constantly force it into the cylinder against said piston to resist a blank holder means actuated movement thereof, said centrifugal pump being in constant and open communication both with said cylinder and said reservoir.

5. In a press of the class described, movable blank holding means, a cylinder, a piston movable in said cylinder and opposing movement in one direction of said means, a fluid supp y reservoir in communication with said cylinder, a centrifugal pump disposed between said reservoir and said cylinder and in constant and open communication with both and operable to constantly apply hydraulic pressure to said piston in one direction, and variable speed means for driving said pump.

6. In a press of the class described, movable blank holding means, a cylinder, a piston working in said cylinder and connected to said means to resist movement thereof in one direction, a fluid supply reservoir surrounding said cylinder, a centrifugal pump having its inlet port in constant and open communication with said reservoir and its discharge port in constant and open communication with said cylinder, and means for operating the pump at variable speeds.

7. In a press of the class described, movable blank holding means, a cylinder, a piston movable in said cylinder and connected to said means to resist movement thereof in one direction, a fluid supply reservoir surrounding said cylinder, a centrifugal pump built into the bottom of said cylinder and having its inlet port in open communication with said reservoir and its discharge port in open communication with said cylinder, and means disposed outside said reservoir to drive said pump.

FREDRICH J. RODE. 

